1. Technical Field
The present invention relates to packaging of a product on a vertical form, fill, and seal machine, and more particularly to forming, filling and sealing a short, wide bag with a product that has an irregular shape, or which does not naturally distribute itself well.
2. Description of Related Art
Form, Fill, and Seal
Vertical form, fill, and seal packaging machines are commonly used in the snack food industry for forming, filling, and sealing bags of chips and other like products. One such packaging machine is seen diagrammatically in FIG. 1. This drawing is simplified, and does not show the cabinet and support structures that typically surround such a machine, but it demonstrates the working of the machine well. Packaging film 110 is taken from a roll 112 of film and passed through tensioners 114 that keep it taut. The film then passes over a former 116, which directs the film as it forms a vertical tube around a product delivery cylinder 118. This product delivery cylinder 118 normally has either a round or a somewhat oval cross-section. As the tube is pulled downward by drive belts 120, the vertical tube of film is sealed along its length by a vertical sealer 122, forming a back seal 124. The machine then applies a pair of heat-sealing jaws 126 against the tube to form a transverse seal 128. This transverse seal 128 acts as the top seal on the bag 130 below the sealing jaws 126 and the bottom seal on the bag 132 being filled and formed above the jaws 126. After the transverse seal 128 has been formed, a cut is made across the sealed area to separate the finished bag 130 below the seal 128 from the partially completed bag 132 above the seal. The film tube is then pushed downward to draw out another package length. Before the sealing jaws form each transverse seal, the product to be packaged is dropped through the product delivery cylinder 118 and is held within the tube above the transverse seal 128.
The material that is fed into the form, fill, and seal machine is typically a packaging film, such as polypropylene, polyester, paper, polyolefin extrusions, adhesive laminates, and other such materials, or from layered combinations of the above. For many food products, where flavor retention is important, a metalized layer will form the innermost layer.
The form, fill, and seal machines are quite expensive, in the range of $250,000 each, but pay for themselves easily when compared to the cost of preformed bags and the machinery to fill them. However, in order to maximize the productivity of the form, fill, and seal machines, it is common for the product delivery tube 118 and former 116 to be made as a unit that is easily interchangeable in less than 15 minutes, so that different size packages can be made by the same machine. The length of the transverse seal can also be changed, by exchanging the sealing jaws, or in some cases, merely by exchanging the facing (the portion of the sealing jaws which actually makes contact with the packaging film). By changing these elements, as well as the width of film roll feeding into the machine and the programming of the machine, one form, fill, and seal machine can handle a number of different products in different size packages, limited primarily by the width of film the machine will handle, the maximum length of bag the machine is designed to handle, and the available former/delivery tube assemblies.
Tube Pack
With some products, it is desirable to package them in tubes, so that they are easily held in one hand. One familiar example is the tubes in which individual servings of ready-to-eat snacks such as peanuts are packaged, shown in FIG. 2. The tube 200 can provide a serving or more of the product, yet by opening on the shorter end, its shape makes it easy to pour out small amounts at a time. The tube 200 for peanuts or similar snacks is manufactured on a vertical form, fill, and seal machine: a narrow tube is formed around an equally narrow delivery tube and a back seal 210, seen in phantom, is formed. The lower transverse seal 212A is formed and the film is pulled. The tube is filled through the shorter end of the tube and the final transverse seal 212B is formed. As can be imagined, filling a long, narrow tube with a given product is a much slower process than filling a wide package with the same product. This is because the product will tend to be slowed by hitting the walls of the delivery tube, as well as by product forming a xe2x80x9cbridgexe2x80x9d across the tube, even if only for a moment. This bridging is worsened when the product is irregularly shaped, or has a tendency to stick together, or where one part of the product is wider that other parts, all of which are true of many snack foods. Additionally, when the opening through which the product is dropped is relatively small, as is the current case in tube packs, the effect is worsened.
Currently, when packaging products into long, narrow tubes, the number of packages produced is much smaller than using the same machine to package into wider bags. This means that more run time is necessary to package a given amount of product, or alternatively, that more packaging machines are necessary to do the job in the same amount of time.
It would be much faster to fill a tube from its longer side, such as a short film draw with a wide transverse seal, but this strategy has its own inherent problems. In this mode, product tends to pile up in the center of the package, leaving the ends unfilled, while the height of product in the center interferes with formation of the final horizontal seal. It is possible to allow additional space at the top of the package so that product does not interfere with forming the seal, but the package produced looks like it was under-filled, especially in comparison to similar products filled in the standard manner.
It would be desirable to find a method of producing tube packs that allows faster throughput, while still providing a well-filled package with a strong seal. Preferably one should be able to do this using the current form, fill, and seal machines, so that no large capital investments are necessary.
Another problem with existing tube packaging affects the consumer, rather than the manufacturer. When a consumer opens a tube package, it would generally be preferable to have the package tear smoothly and easily across the small end of the tube, as this creates an ideal small opening for controlling the rate of pouring of the snack foods. This has, however, been difficult to achieve.
In the current tube packages, the best method has been to provide a small cut 216 into the top transverse seal 212B. However, once the consumer tears through the seal, the tear is as likely, or more likely, to continue down the side of the tube as it is to neatly tear across the top of the tube.
Many packaging processes utilize oriented polymers. These are long-chain polymers that have been stretched and treated until the polymer has a specific alignment or orientation. When one or more layers of an oriented polymer are used in the thin films for snack packages, a cut or tear that runs parallel to the orientation will tend to tear in the direction of the orientation, although this will not be true of a cut that goes across the orientation of the polymers. Using an oriented polymer can thus help, in many applications, to achieve a cleaner tear. However, where a tear must start in one direction (downward across the top seal) and it is desirable to change the direction of the tear (to parallel to the seal), oriented polymers cannot help. Thus, it would also be desirable to have a better method of opening the tube.
In the present invention, tube packs are produced using a short pull length and a wide transverse seal, so that the product is delivered through the longer side of the tube. Rather than the traditional round or oval delivery tube, the innovative delivery tube has an almost rectangular shape, although the ends have a radius of curvature rather than a flat shape. Preferably, the delivery tube has one or more product diverters that cause the product to be spread evenly across the package. In some embodiments, an optional vibrator can be added to the former/delivery tube assembly, to help the product settle in the tube prior to sealing. Because the product is spread across the length of the package, the final seal can be formed without interference. Various embodiments of the invention will have one or more of the following advantages:
throughput is increased, saving both time and money;
effective seals are maintained;
packages are comparably filled to older methods of packaging tubes;
tube packs are produced on standard form, fill, and seal (FFS) machines, requiring only new former/delivery tube assemblies.
allows for a larger face panel;
allows better means of opening; and
allows a compact multi-pack of product simply by altering the programming of the FFS machine.